Process of treating lime.



UNITED STATES PATENT OFFICE.

HENRY P. DODGE, OF TOLEDO, OHIO.

PROCESS OF TREATING LIME.

SPECIFICATION forming part of Letters Patent No. 671,621, dated April 9, 1901.

Application filed February 15, 1900. serial No. 5.372. (No specimens.)

T0 aZZ whom, it may concern:

Be it known that I, HENRY P. DODGE, a citizen of the United States, residing at Toledo, county of Lucas, and State of Ohio, have invented a certain new and 'useful Process of Treating Lime, of which the following is a specification.

My invention has for its object the economical production on a commercial scale of slaked lime in a pulverulent form capable of being kept for considerable periods of time in ordinary receptacles or in the open air without liability of spontaneously caking, swelling, or otherwise changing its form or condition.

' The invention consists in the art, mode, or method, hereinafter set forth, of treating fresh-burned lime whereby these results are attained.

With a view to rendering more clear the mode of treatment, the reasons for the several steps, and the distinctions existing between this and other plans adopted or proposed some preliminary observations are deemed proper. Lime varies considerably in its chemical composition, particularly in regard to the proportion of magnesia present. Lime containing a considerable percentage of magnesium-say twenty-five per cent. or over-even when reduced to a granular or to a pulverulent condition if exposed to contact with water for a time acts in a manner similar to so much sand and may be stirred and mixed with the water in a way to expose all particles thereto and to cause each to be coated with a thin film thereof. The period necessary to such coating varies from about one minute to about five minutes, according to the character of the lime, the size of its particles, and, perhaps, other considerations not so apparent or perfectly understood. After the lapse of such period of time, however, a chemical action begins, the lime undergoing change from an oxid to a hydrate. When this change is fairly begun, it is impracticable to readily stir or agitate the particles and present them separately to the water, because the oxids of lime and of magnesia take up more water than is required to completely satisfy the molecular change. Some portions of the mass become unduly wet and pack together and others do not receive sufficient water unless more be present than is necessary to complete hydration. Where the percentage of magnesium is smaller than above indicated, the period during which the stirring or agitation of the lime in the presence of or in contact with water may be performed is shorter. To insure uniformityin treatment and in the resultant product, it is necessary that the particles be quite small and as nearly uniform in size as possible, because, owing to the capacity of lime to take up more moisture than is requisite for its conversion into a hydrate, smaller particles would be more speedily permeated by the Water than larger ones and continuing to absorb Water they would become so charged that, although not appearing wet to the eye, they would, nevertheless, pack and cake subsequently, while the larger particles would be robbed of water needed to complete their hydration. Owing also to the longer time required to permeate the larger particles, they would contain after treatment considerable quantities of unconverted oxid or unslaked lime, and hence would i be liable to swell and burst and to rupture the containing-package.

From the foregoing it will be apparent that the fresh-burned lime to be slaked should be in a state of somewhat fine subdivision and the particles should be as nearly uniform as practicable. It will further be seen that because of the necessity of thoroughly stirring, mixing, or agitating the lime and water before the chemical conversion begins or proceeds with any considerable activity it is desirable to employ lime containing a reasonable percentage of magnesium. On the other hand, absolute uniformity of size is of course unattainable, and a reasonable range or variation is permissible. So, too, as different methods of agitation may effect exposure of all the particles to water with different degrees of rapidity the presence of magnesium in the indicated quantity or in any material quantity may in some instances prove unnecessary. In view of these facts it is to be understood that the process hereinafter specifically described is not restricted to treatment of lime containing magnesia in the proportion indicated or in any considerable quantity nor to the preliminary crushing or reducing of the lime as a step in the process of treatment, it being possible to obtain from the kilnand from the repeated handling of the lime a very considerable quantity of fine material, which, being properly sifted or screened, may be treated without previous special crushing or reduction. Having thus explained in a general way these'm'atters, I will describe specifically the process practiced by me and found effective and satisfac tory, observing in this connection that the lime used by me has contained, approxi mately, forty per; cent. of the OXld'Of magnea sium, being produced from a limestone found in the State of Ohio and commonly known as dolomite or dolomitic limestone.

In carrying outmy invention I'preferably take the bullelime just asit is drawn from= the kilnsafterburning in lum'psof varying sizes and grind, crush, or otherwise' rediiceitto afine powder: The 'powder'so prod needis a'dvisablyscreened or sifted'tetake out i any particles not sufficiently reduced-'and to insure 'an-even' grading-ofthe lime. A -m eas-'- ured qua'n'tity-of the powderor fine granular mass-is thensubjected tora'pid stirring or agitation in'asuitablevat or'tank', and water i isadded while the agitation proceeds: The quantity of water used isto be accurately determined and must hear'a' de'finite relation to=thequantity of limetre'ate'd: The rela tive proportions-in ayand 'will vary so'me'what according to" the "chemical composition oftheliinez- With alime of'the character a'bove noted and-con tai-ningabout thirtyl=to-forty"'per cent: of"-inagnesiuinoxid- I find it advisable' to-u-se abou-t=one to one an'done-halfiquartsof watei to every' five poundsofi lime. T-h'e proportion is based upon the quantity'of Water nec es'sa'ry to convert all the lim"e*from anoxid to a' hydrate, anditis important that theproper proportion be nicely determined'and accu= rate'ly' observed; Owing to the rapidand thorough agitation of the mass of lime, all its 7 particles are-exposed orsubjected'to the wa ter, which accordingly coa'ts each and every particle or" permeates the same andgives to ea'ch part'icle the'quantitynec'essary to effect itshydratio nor chemical cdnve'rsion; A very s-lights'urplus of water may be usedwithout" ter and'the'whole subjected to rapid and thorough agitation; butitis preferred' to add the water to the lime and to supply it gradually; yetwithsufficientrapiditytO enable the moistening'of all the particles-to be effected before the chemical conversion begins onproceeds to anyconsiderable extent.- The mass thus treated is now allowed to stand until cold, the great heat produced by the chemical action incident to conversion taking up and evaporating any remaining moisture and leavingthe mass in a dry state and capable of usewitho ut furthertre'atment. To insure greater uniformity and to remove any bits of unburnedstone, sticks, nails or other foreign matter commonly found in the mass, it is ad- 'vis'able when the same is completely cooled ,and dried to sift the lime through a fine screen or sieve or to pass it through crushing *orreducingrnechanism capable of reducing 'to'fine powder any hard particles present.

The time required to efiect hydrationva ri'es somewhat :according to' the quality or ichara'c'ter'offi the lime; but with lime of the character above noted thr'ee --mini1teswill oridinarily s'u'flicei The time required for cooling-depends so mewhat upon the temperature of the coolingfroom,atmospheric conditions;ai1'd 'th'elikegbut Ifrom twelve to thi rtysix" hours covers the usual range-J- ;above described ma'y be used commercially in all 'pla'c'es "where* quick-1i me c'an be used-ahd in*1ik'e="1nanner It'retains' its setting pro'pjerties; but, unlike quicklime, it does not'swel-l [DOPdOe'S it air--s=lake,-and upon heing-fmiired {with-water it'does not produce-heat! The ipro'duct is found to ans-Wei" admirab'ly' th'e purposes of quicklime and possesses thead without undergoing chemical change, with ;out solidifying or caking; and without-ex- ;p'a'nding; This latter'capability is evidenced by the fact that for anitmberof menths the I prepared lirn'e hasbeen placedupon-the mar- 'jket-=in'paper hags'and in no case has it burst the packages orso'lidified.

The present invention is to be clearly-dis- -tingnished from the "plans'or methodso f pre I paringlinie which involve'the treatmentthe're of in the fo'rm' of lumps ot considerable size or varying materially:or appreciably in bulk;

, since; as already explained, it' is-=imp'racticable toattain uniformity 'und'ersuch condi-' tions or to reach and wet theinterior'portions of lumps ofany considerahle size before the chemical action' becomes vigorous Sogt'oo, it is to be distin'g-uished from any processor niode of treatmentinvolvingthe total immec sion' of lo m=ps'and their? r'etention for a considerable orappreciable time under water, since' byreason ofthe avidity 'of lim'efo'r Wate'r the lumps or particles 'wnrtakeup water inexcessof the quantity necessary to effect conversion to hyd rate and willretainsuf- 'ficient moisture to cause a cahing 'orpacking of the lime subsequently;

It ispartic'ularly: to beobserved that" the operation-or treatment here set forth iseffected'in the open atmospher'eand' that any ICO Vapor produced is allowed to pass off freely. Hence there is entire freedom from danger through excessive pressures and there is no uncertainty as to the quantity of moisture supplied to the lime. The lime thus prepared is peculiarly white and clear.

Having thus described my invention, what I claim is- 1. The herein-described method of treating lime, which consists in reducing fresh-b urned lime to a fine granular or pulverulent condition; agitating, the mass, and, while in a state of agitation, exposing its particles to water in quantity sufficient to effect hydration; permitting the mass to cool, and subsequently sifting or screening the same.

2. The herein-described method of treating lime, which consists in subjecting, in the open air, fresh-burned lime in the form of fine particles or powder, to agitation in the presence of water in quantity sufficient to effect its conversion into a hydrate, but not materially in excess of such quantity; and permitting the mass after such hydration to cool and assume a dry pulverulent form.

3. The process of treating lime, which consists in subjecting the same, while in a granular or pulverulent condition, to vigorous agitation in the presence of water sufficient to effect complete hydration but not appreciably in excess thereof; permitting the mass to cool; reducing the same to pulverulent form; and screening or sifting the powdered mass to remove any particles of undue size. In testimony that I, HENRYP. DODGE, claim the foregoing as my own I hereto affix my signature in the presence of two witnesses.

HENRY P. DODGE.

Witnesses:

H. H. BRAND, WM. K. TERRY. 

